In the land mobile communication, there are a plurality of propagation paths from a transmitting point to a receiving point, and a received wave is a synthesized wave composed of a plurality of waves with different propagation paths. For this reason, radio waves transmitted from a transmitting point at the same time are turned to a plurality of signal waves, which are propagated through a plurality of paths. As a result, these waves reach at a receiving point with some deviation over time, and they reach the receiving point while interfering with each other. To eliminate this, path separation is performed by utilizing property of data diffusion in the spread spectrum radio transmission, and the separated signals are synthesized and path synthesizing gain is obtained to improve the receiving characteristics.
In a conventional type spread spectrum radio transmitter and receiver having RAKE receiving functions to eliminate the influence of multi-path as described above comprises, as shown in FIG. 22, a receiving antenna unit 2201, a high frequency unit 2202 for converting a signal received by antenna to a signal of intermediate frequency band, an orthogonal detection unit 2203 for picking up baseband signal from signals of intermediate frequency band, and a RAKE receiver 2210 for carrying out signal processing to eliminate influence of multi-path. The RAKE receiver 2210 comprises an inverse diffuser for performing inverse diffusion to the received signals, delay adjusters 2212-1 to 212-K for adjusting time delay of the signal obtained by path separation, amplification factor variable amplifiers 2213-1 to 2213-K, a propagation path coefficient controller 2214 for controlling amplification factor of each of the amplification factor variable amplifiers 2213-1 to 2213-K, and a RAKE receiving unit adder 2215 for synthesizing signals of each path. In the present application, the terms "antenna" and "adaptive antenna" are applied to those of general concept, while the terms "antenna unit" and "adaptive antenna unit" indicate concrete components respectively.
In a conventional type receiving device, radio wave is received first by the receiving antenna unit 2201, and the received signal is converted to a signal of intermediate frequency band by the high frequency unit 2202. The orthogonal detection unit 2203 picks up a baseband signal by orthogonal detection of the signal of intermediate frequency band. The baseband signal is inversely diffused by an inverse diffuser 2211. On the inverse diffuser 2211, inverse diffusion processing practiced in CDMA (Code Division Multiple Access) is performed, i.e. correlative processing is performed for the received signal and diffusion signal, and only highly correlative components of the received signal are left, and delayed wave having delay time greater than chip time width of diffusion signal is detected. Then, at the delay adjuster 2212-m, delay time is compensated and unnecessary signals are removed according to delay time. Phase adjustment by such signal processing and processing of the phase not adjusted here in the subsequent stage by an amplifier are generally practiced in RAKE receiving. The amplitude of output of the phase adjustment delay adjuster 2212-m is adjusted at the amplification factor variable amplifier 2213-m for each of path "m", and path synthesizing is performed at the RAKE receiving device adder. Here, m represents an integer of 1 to K and is also used to indicate one of paths from the first path to the K-th path. At the propagation path coefficient controller, amplification factor of the amplification factor variable amplifier 2213-m is controlled according to the output of the inverse diffuser 2211.
However, in the RAKE receiving unit of the conventional type spread spectrum radio transmission receiving device, signal processing to match multi-path is performed based on the signal after inverse diffusion. Accordingly, processing can be performed on delay wave greater than chip time width of diffusion signal, and it cannot be performed on the delay wave having delay time smaller than chip time width.
Also, in the conventional type spread spectrum radio transmitter and receiver, the smaller the co-channel interference wave (including interference with other station) is, the higher the receiving characteristics are. Therefore, it is necessary to eliminate co-channel interference wave as far as possible.